From: Will Deacon <will@kernel.org>
To: Jiping Ma <jiping.ma2@windriver.com>
Cc: mark.rutland@arm.com, alexander.shishkin@linux.intel.com,
catalin.marinas@arm.com, will.deacon@arm.com,
linux-kernel@vger.kernel.org, acme@kernel.org,
peterz@infradead.org, mingo@redhat.com, namhyung@kernel.org,
jolsa@redhat.com, linux-arm-kernel@lists.infradead.org
Subject: Re: [PATCH] Perf: support to unwind userspace application stacks generated with thumb.
Date: Thu, 16 Apr 2020 08:10:24 +0100 [thread overview]
Message-ID: <20200416071023.GB29742@willie-the-truck> (raw)
In-Reply-To: <20200416053829.130395-1-jiping.ma2@windriver.com>
On Thu, Apr 16, 2020 at 01:38:29PM +0800, Jiping Ma wrote:
> Only push sp and lr in the stack for thumb mode. it will go
> through the stack find sp and lr.
>
> Change this to the more detailed description of the patch
>
> Signed-off-by: Jiping Ma <jiping.ma2@windriver.com>
> ---
> arch/arm64/kernel/perf_callchain.c | 36 +++++++++++++++++++++++++++---
> 1 file changed, 33 insertions(+), 3 deletions(-)
>
> diff --git a/arch/arm64/kernel/perf_callchain.c b/arch/arm64/kernel/perf_callchain.c
> index bcafd7dcfe8b..97dde271c121 100644
> --- a/arch/arm64/kernel/perf_callchain.c
> +++ b/arch/arm64/kernel/perf_callchain.c
> @@ -104,6 +104,30 @@ compat_user_backtrace(struct compat_frame_tail __user *tail,
>
> return (struct compat_frame_tail __user *)compat_ptr(buftail.fp) - 1;
> }
> +
> +void
> +user_backtrace_thumb(struct perf_callchain_entry_ctx *entry,
> + struct pt_regs *regs)
> +{
> + u32 sp;
> + u32 *sp_t;
> + /*
> + * Only push sp, lr to stack.
> + */
> + for (sp = regs->compat_sp; (sp < current->mm->start_stack) &&
> + (entry->nr < entry->max_stack); sp += 4) {
> + sp_t = (u32 *)(unsigned long)sp;
> + if ((*sp_t > regs->compat_sp) &&
> + (*sp_t < current->mm->start_stack)) {
> + if (*(sp_t + 1) < current->mm->end_code &&
> + *(sp_t + 1) > current->mm->start_code) {
> + perf_callchain_store(entry, *(sp_t + 1)-1);
> + sp += 4;
> + }
> + }
> + }
> +}
This looks like a pile of fragile heuristics to me. Why don't you just use
libunwind in userspace, the same way you'd have to if you compiled without
framepointers?
Will
_______________________________________________
linux-arm-kernel mailing list
linux-arm-kernel@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-arm-kernel
next parent reply other threads:[~2020-04-16 7:10 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <20200416053829.130395-1-jiping.ma2@windriver.com>
2020-04-16 7:10 ` Will Deacon [this message]
[not found] ` <01029876-e167-a1ba-cb1a-d97adf23dde4@windriver.com>
2020-04-22 8:19 ` [PATCH] Perf: support to unwind userspace application stacks generated with thumb Will Deacon
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20200416071023.GB29742@willie-the-truck \
--to=will@kernel.org \
--cc=acme@kernel.org \
--cc=alexander.shishkin@linux.intel.com \
--cc=catalin.marinas@arm.com \
--cc=jiping.ma2@windriver.com \
--cc=jolsa@redhat.com \
--cc=linux-arm-kernel@lists.infradead.org \
--cc=linux-kernel@vger.kernel.org \
--cc=mark.rutland@arm.com \
--cc=mingo@redhat.com \
--cc=namhyung@kernel.org \
--cc=peterz@infradead.org \
--cc=will.deacon@arm.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox